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StringBuilder indexOf() method in Java with Examples
  • Last Updated : 22 Nov, 2019

In StringBuilder class, there are two types of indexOf() method depending upon the parameters passed to it.

indexOf(String str)

The indexOf(String str) method of StringBuilder class is the inbuilt method used to return the index within the String for first occurrence of passed substring as parameter. If substring str is not present then -1 is returned.

Syntax:

public int indexOf(String str)

Parameters: This method accepts only one parameter str which is String type value and refers to the String whose index is required.

Return Value: This method returns the index of the first occurrence of the passed substring, or -1 if there is no such substring present.



Below programs illustrate the StringBuilder.indexOf() method:

Example 1: when passed substring is present in the sequence.




// Java program to demonstrate
// the indexOf() Method.
  
class GFG {
    public static void main(String[] args)
    {
  
        // create a StringBuilder object
        // with a String pass as parameter
        StringBuilder str
            = new StringBuilder("GeeksForGeeks");
  
        // print string
        System.out.println("String contains = " + str);
  
        // get index of string For
        int index = str.indexOf("For");
  
        // print results
        System.out.println("index of string 'For' = "
                           + index);
    }
}
Output:
String contains = GeeksForGeeks
index of string 'For' = 5

Example 2: when passed substring is not present in the sequence.




// Java program to demonstrate
// the indexOf() Method.
  
class GFG {
    public static void main(String[] args)
    {
  
        // create a StringBuilder object
        // with a String pass as parameter
        StringBuilder str
            = new StringBuilder(
                "Geeks for Geeks contribute");
  
        // print string
        System.out.println("String contains = "
                           + str);
  
        // get index of string article
        int index = str.indexOf("article");
  
        // print results
        System.out.println("Index of string"
                           + " 'article' = "
                           + index);
    }
}
Output:
String contains = Geeks for Geeks contribute
Index of string 'article' = -1

indexOf(String str, int fromIndex)

The indexOf(String str, int fromIndex) method of StringBuilder class is the inbuilt method used to return the index within the String for first occurrence of passed substring as parameter starting at the specified index ‘fromIndex’. If substring str is not present then -1 is returned. fromIndex is Integer type value refers to the index from which to start the search. The index returned by this method is calculated from the start of the sequence only difference is that index of the start of the search is given in this method. if string present before the index of the start of search but not after then -1 will return.

Syntax:

public int indexOf(String str, int fromIndex)

Parameters: This method accepts two parameters:



  • str: which is String type value refers to the String whose index is required.
  • fromIndex: which is Integer type value refers to the index from which to start the search.

Return Value: This method returns the index of the first occurrence of the passed substring starting at the specified index, or -1 if there is no such substring present.

Below programs illustrate the StringBuilder.indexOf() method:

Example 1: when passed substring is present in the sequence.




// Java program to demonstrate
// the indexOf() Method.
  
class GFG {
    public static void main(String[] args)
    {
  
        // create a StringBuilder object
        // with a String pass as parameter
        StringBuilder str
            = new StringBuilder("GeeksForGeeks");
  
        // print string
        System.out.println("String contains = " + str);
  
        // get index of string Form index 3
        int index = str.indexOf("For", 3);
  
        // print results
        System.out.println("index of string"
                           + " \"For\" = "
                           + index);
    }
}
Output:
String contains = GeeksForGeeks
index of string "For" = 5

Example 2: when passed substring is present in the sequence but index of search is greater than index of substring.




// Java program to demonstrate
// the indexOf() Method.
  
class GFG {
    public static void main(String[] args)
    {
  
        // create a StringBuilder object
        // with a String pass as parameter
        StringBuilder str
            = new StringBuilder("Geeks for Geeks contribute");
  
        // print string
        System.out.println("String contains = " + str);
  
        // get index of string Geeks from index 15
        int index = str.indexOf("Geeks", 15);
  
        // print results
        System.out.println("index of string 'Geeks ' = "
                           + index);
    }
}
Output:
String contains = Geeks for Geeks contribute
index of string 'Geeks ' = -1

References:

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